Cp*Ir^III‐Catalyzed [3+2] Annulations of N‐Aryl‐2‐aminopyrimidines with Sulfoxonium Ylides to Access 2‐Alkyl Indoles Through C–H Bond Activation

Abstract

The iridium‐catalyzed aromatic C–H alkylation followed by intramolecular annulation reactions between N‐aryl‐2‐aminopyridines and sulfoxonium ylides for the synthesis of 2‐alkyl indoles is described. This highly efficient and step‐economical cyclization reaction displays excellent functional group compatibility and regioselectivity. Afterwards, the directing group in C–H alkylation can be readily removed to obtain the free N–H indoles. Thus, the sulfoxonium ylide, a carbene precursor, is proved as a useful surrogate of diazo compounds in C–H activation chemistry.

Recent Advances in Metal‐Catalyzed C−H Bond Functionalization Reactions of Sulfoxonium Ylides

“… [58] Wu group also published an efficient methodology for the synthesis of 2‐alkylindoles via C−H activation of N ‐aryl‐2‐aminopyrimidines by a cation Cp*Ir(III)‐complex and subsequent [3+2] annulation with sulfoxonium ylides (Scheme 54). [59a] Similar report was also found for iridium(III)‐catalyzed C−H functionalization of N ‐phenylpyridin‐2‐amines with sulfoxonium ylides under mild reaction conditions [59b] …”

Ruthenium(II)-Catalyzed Homocoupling of α-Carbonyl Sulfoxonium Ylides Under Mild Conditions: Methodology Development and Mechanistic DFT Study

“…It was generally proposed that the cyclic product was formed by the first generation of an acylmethylation intermediate in similar cascade reactions. (Chen et al, 2018;Hu et al, 2018aHu et al, ,b, 2019Liang et al, 2018;Shi et al, 2018;Xiao et al, 2018;Xie et al, 2018bXie et al, , 2019Xie H. et al, 2018;Xu et al, 2018;Zhou et al, 2018;Cai et al, 2019;Chen P. et al, 2019;Cui et al, 2019;Huang et al, 2019;Lai et al, 2019;Liu et al, 2019;Luo et al, 2019;Lv et al, 2019;Nie et al, 2019;Shen et al, 2019;Wu C. et al, 2019;Zhang et al, 2019Zhang et al, , 2020Wu et al, 2020). Further transformations from IM6 were explored theoretically to confirm whether the acylmethylation intermediate (IM8) is key in the formation of 2a (Figure 2).…”

α-Carbonyl sulfoxonium ylides in transition metal-catalyzed C–H activation: a safe carbene precursor and a weak directing group

“…The kinetic isotope experiment ( k H / k D = 1.2) indicated that Ir( iii )-catalyzed C–H activation may not be the rate-determining step (Scheme 60a). Similarly, Wu's 64 group disclosed an Ir( iii )-catalyzed [3 + 2] annulation of aniline derivatives with sulfoxonium ylides via C–H activation. Besides pyrimidine, other N-containing heterocycles, such as pyrazine, pyridazine, and pyridine were employed as directing groups in this transformation to form 2-substituted indoles (Scheme 60b).…”